apg_typeside t apg_instance G1 : s apg_instance G2 : s apg_instance G : s apg_morphism h : G1 -> G2 apg_morphism h' : G1 -> G2 apg_morphism k : G2 -> G ---------------------------------- apg_morphism (coequalize_u h h' k) : coequalize h h' -> GCoEqualizer universal property mediating morphism of two parallel morphisms in the category of APGs.